(a) Field of the Invention
The present invention relates to carbo-nitrided case hardened martensitic stainless steels which have utility in bearings and gears for aerospace mechanical systems including gas turbine engines and rocket engines.
(b) Prior Art
Bearings and gears are routinely manufactured from stainless steel materials, some of which are routinely carburized case hardened. Such carburization results in the formation of hard carbides and a hard carbon rich martensite matrix necessary for bearing and gear load bearing capability. In the case of martensitic stainless steels, such carburization results in the formation of chromium rich carbides that deplete the steel matrix of chromium that is necessary for corrosion resistance. The depletion of the chromium is problematic because the desired protective Cr2O3 oxide, which creates the stainless behavior, is not formed as a continuous impervious barrier between the base metal and the environment (air, water, etc.).